1. Field of the Invention
The present invention concerns a rubber composition containing a powdered leather and molding products obtained therefrom, which can be utilized for sports goods such as grips for tennis rackets, badminton rackets, golf clubs and baseball bats, wearing goods such as gloves, raincoats and caps made of rubber, vehicle parts such as grips for handle bars of motorcycles, window frame rubbers, wiper rubber, rubber vibration insulators, braking rubber, grips for shift levers, interior automotive trims and tires, building materials such as anti-slip members and sound absorbers, shoe goods such as rubber shoes and shoe soles, as well as domestic electric products, writing utensils, furniture and musical instruments.
2. Description of the Related Art
In the rubber composition containing a natural powdered leather and the molding product obtained by the prior art as described above, however, white powder is formed on the surface during use or storage for a long period of time, in particular, after being left for a long period of time in a highly humid atmosphere, to deteriorate the performance and the quality (appearance) of goods. In particular, if a natural powdered leather of small grain size, for example, of less than 250 .mu.m is used, the white powder comes out remarkably.
Further, in the case of fabricating grips of sports goods by using the rubber composition containing a natural powdered leather with a small average grain size, for example, of less than 10 .mu.m, if the surface of the grip is polished for enhancing the shape of the surface, there is a problem that the moisture absorption of the powdered leather is somewhat reduced and the anti-slip effect is decreased though the powder content is identical, to worsen the overall balance of characteristics.
An object of the present invention is to provide a rubber composition containing a powdered leather and a molding product free from occurrence of the white powder and having excellent enduring performance and quality.
In accordance with the present invention, it is intended to achieve the foregoing object, in producing a molding product by using a rubber composition containing a powdered leather, while taking notice on the fact that occurrence of the white powder is prevented by using a fine powdered leather of a specific grain size and with less impurity.
The rubber composition containing a powdered leather according to the present invention is a dispersion mixture comprising from 10 to 400 parts by weight of a powdered leather with a skin component of greater than 75% by weight, a total amount of Na.sup.+ ions and Ca.sup.2+ ions extractable with water of less than 0.5% by weight and with an average grain size D.sub.50 from 10 to 250 .mu.m, and 100 parts by weight of a rubber.
The rubber molding product containing a powdered leather according to the present invention is formed by using, as the main ingredient, the rubber composition containing the powdered leather as described above.
The rubber composition containing the powdered leather and the molding product according to the present invention basically comprises a rubber and a powdered leather dispersed therein in a dot-like pattern.
In the composition and the molding product of the aforementioned type, the amounts of the powdered leather material and the rubber material used are from 10 to 400 parts by weight and 100 parts by weight respectively. If the ratio of the powdered leather exceeds 400 parts by weight, it makes the kneading and stirring difficult in the composition, to render it impossible for homogeneous dispersion thereby embrittling the molding product. On the contrary, if it is less than 10 parts by weight, the addition effect, that is, the moisture absorbing/releasing property or the like becomes insufficient.
The reasons for defining the values for the properties of the powdered leather in the composition and the molding product according to the present invention will be shown below.